1. Field of the Invention
The present invention relates to an electric motor apparatus driving an electric motor by a driving circuit and a power steering system controlling a steered angle of a steered wheel separated mechanically from a steering angle of a steering wheel in a vehicle by the electric motor apparatus on a basis of a steering angle of a steering wheel.
2. Description of the Related Art
It is recently developed a power steering system, so called steer by wire system controlling a position of a steered angle of a steered wheel separated mechanically from a steering angle of a steering wheel in a vehicle by means of an actuator such as an electric motor on a basis of a steering angle of a steering wheel. It is typically known for this kind of the power steering system providing two actuators for a fail-safe function at an abnormal condition of the actuators as disclosed in for example Japanese Patent Laid-open Publication No. 2002-37112.
In the above-mentioned related art of the power steering system, since there are two actuators, a total cost is increased and a total size of all of an electric motor apparatus and the steering system become large.